JPH0312354Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] This invention relates to the air cap of an air spray gun for painting, and is intended to prevent atomized paint from adhering to the front surface of the air cap.

[Prior Art] The air cap of an air spray gun vigorously injects compressed air from the front of the cap, atomizing the paint and directing it toward the object to be coated. but,
Depending on the shape of the air cap, surrounding air is drawn in near the spout, creating a vortex, which simultaneously draws in fine particles of atomized paint and deposits them on the front surface of the air cap.

For this reason, it has already been proposed to form a cone around the injection port, especially the central air hole for atomization, which has a large amount of air, to reduce the generation of vortices due to air entrainment (Utility Application No. 58-29474). . However, this problem has not yet been solved in the air cap and the paint nozzle that engages with the air cap, which employs a spherical sheet system as shown in FIG. That is, in the case of the air cap shown in FIG. 6, the sheet portion 1 has a sheet formed on a spherical surface with respect to the center of the paint jetting nozzle 2,
In order to maintain concentricity with the central air hole 3, it has an optimal structure for a spray gun that requires precision. In this system, it is also an important condition to make the diameter of this spherical surface smaller, so the distance between the front end and the outer peripheral surface of the air cap is shortened. Therefore, when the air cap surface is formed in a conical shape from the center, the parallel surface 4 remains until it reaches the outer periphery. Since this parallel surface 4 is in a state of protruding forward from the conical surface, a vortex is generated and conditions for paint adhesion are worsened. In addition, an air hole 1 made in the corner 13'
4' is machined to have a flat or concave surface,
When air is injected, turbulent vortices are also generated on the opening surface, causing paint to adhere.

[Problems to be solved by the invention] As described above, in an air cap that uses a conventional spherical sheet, atomized paint particles are trapped in the air cap, especially at the corners, due to the turbulent vortices that occur over the entire surface of the air cap. When used for a long time, the semi-dry adhered paint is blown away and adhered to the object to be coated, often resulting in poor coating. Therefore, it was necessary to interrupt the painting work and clean it within a relatively short period of time.
The purpose of the present invention is to solve this problem by providing an air cap that allows continuous painting for a longer period of time.

[Means for solving the problem] In order to solve the above-mentioned problem, the present invention makes the front surface of the air cap in which the central air hole is formed a conical shape, and the front surface of the air cap, in which the central air hole is formed, is shaped like a cone. The shape has no protruding parts. Furthermore, the opening surface of the jet nozzle was designed to have a streamlined cross-sectional shape at the corners where adhesion is likely to occur. It has been found through experiments that the conical shape is best formed with an angle in the range of 130° to 140°.

[Operation] When spraying with the air cap configured according to the present invention, air near the air holes is also sucked in by the compressed air injected from each air hole. For this reason, the surrounding air is sucked toward the airflow, but in the case of this invention, the suction airflow flows in a laminar flow along the conical surface, creating turbulent eddies in front of the front and corners. This prevents atomized paint particles from adhering to the air cap surfaces, including the corners.

[Example] Figures 1 to 3 show an example of the present invention, and Figure 1 is a sectional view of the tip of the spray gun;
Figure 2 is a front view of the air cap, Figure 3 is a cross-sectional view of Figure 2, Figure 4 is a cross-sectional view of Figure 1, and Figures 5a and b correspond to Figure 4. Examples are shown below.

A paint nozzle 6 is provided at the tip of the spray gun body 5, and a paint valve 8 is provided to move forward and backward inside a spout 7 formed at the center of the tip. The air cap 9 is engaged with the paint nozzle 6 at a seat 10, and is detachably secured to the main body 5 by a cover 11. These structures are already known.

The air cap 9 has a central hole 1 around the spout 7.
2 is formed, and compressed air is injected from between the paint nozzle 6 and the tip of the paint nozzle 6 to atomize the paint. Corners 13 are provided on both sides of this center hole, and side air holes 14 are provided here. This side air hole 14
is for forming a spray pattern.
The drilled surface of the center hole 12 is a conical surface 15 that widens toward the rear, and when this conical surface 15 is extended beyond the outer circumferential edge of the air cap 9, its forwardly protruding portion extends beyond the corner portion 13. Form it as if it were nothing. Therefore, if the conical surface 15 extends to the outer periphery of the air cap 9 at the same angle, the front surface of the cover 11 located on the outer periphery will reach the conical surface 15.
It is necessary to prevent it from protruding forward beyond the extended surface of the In this embodiment, the angle of the conical surface 15 is formed at 138 degrees, but it may be in the range of 130 degrees to 140 degrees, and the optimum angle varies slightly depending on other conditions.

Further, the corner portion 13 projecting forward is formed such that the surface in which the side air hole 14 is formed forms an arc-shaped tip end portion of a cross section in which both side surfaces of the corner portion 13 are connected in a streamlined shape. For this reason, the flow of the entrained air becomes smooth, and no eddies occur at the tips of the air holes.

[Effects of the invention] As described above, according to the invention, even if paint is continuously sprayed from a spray gun for a long time, the amount of paint that adheres to the front surface and corners of the air cap is lower than that of a conventional air cap. Compared to the air cap shown in Figure 6, it took more than 10 times as long to achieve the same level of paint adhesion. Therefore, maintenance during painting work has been greatly reduced, and it has become possible to paint for hours without worrying about paint defects.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a spray gun showing one embodiment of the present invention, Fig. 2 is a front view of the air cap, Fig. 3 is a cross-sectional view of Fig. 2, and Fig. 4 is a cross-sectional view of Fig. 1. - shows a cross-sectional view; Further, FIGS. 5a and 5b show other embodiments corresponding to FIG. 4, respectively. FIG. 6 shows a conventional case, and the air cap is a sectional view corresponding to FIG. 3 of the present invention, and FIG. 7 is a sectional view corresponding to FIG. 4. 6... Paint nozzle, 7... Spout, 9... Air cap, 12... Center hole, 13... Corner, 15
...conical surface.

Claims (1)

[Claims for Utility Model Registration] 1. An air spray gun that has a central air hole for atomization around the ejection opening of a paint nozzle, and a corner portion having side air holes for pattern formation on both sides of the air hole. The air cap is provided with a spherical sheet approximately centered on a central air hole at the rear of the air cap, wherein the tip surface of the central air hole has a conical shape that expands rearward, and the conical surface is extended. An air cap for an air spray gun, which is configured so that it does not protrude beyond the corner other than the above-mentioned corner, and has a shell-shaped cross section on the face on the outlet side of the corner where the side air hole opens. 2. The air cap for an air spray gun according to claim 1, wherein the angle of the conical surface is 130° to 140°.